Self-attaching female fasteners, including pierce and clinch nuts, are limited in application by a range of panel thicknesses. A self-attaching nut typically includes a projecting pilot portion and a flange portion on at least opposed sides of the pilot portion having a generally planar panel support face generally parallel to the end face of the pilot portion and a groove in the panel support face of the flange portion adjacent the pilot portion. The self-attaching nut may be utilized as a pierce nut, wherein the panel is supported on a die member in a die press having a projecting piercing or clinching lip configured to be received in the groove in the panel support face of the flange portion and the projecting pilot portion is driven against the panel, piercing an opening in the panel, which receives the pilot portion therethrough, and the projecting piercing lip then drives a panel portion adjacent the panel opening into the groove of the pierce nut, forming a mechanical interlock between the panel and the pierce nut permanently attaching the pierce nut to the panel. The self-attaching female fastener or nut may also be utilized as a clinch nut, wherein a panel opening configured to receive the pilot portion is preformed in the panel and the clinching nut of the die button deforms the panel into the groove in the same manner as a pierce nut.
A self-attaching female fastener may be formed in a rolling process, wherein steel rod is rolled into the desired cross-sectional configuration of the self-attaching female fastener, cut to length and pierced through the pilot portion forming a bore and the bore may be tapped to form a female thread depending upon the application. Alternatively, the bore may be smooth to receive a thread forming or thread rolling male fastener. As will be understood by those skilled in this art, a rolled self-attaching female fastener or nut will have a generally rectangular configuration, as disclosed for example in U.S. Pat. No. 4,971,499 assigned to the predecessor in interest of this application, wherein the pilot portion includes a rectangular end face, the flange portions are on opposed sides of the pilot portion each having a rectangular panel support face and the grooves are linear. In the self-attaching female fastener disclosed in U.S. Pat. No. 4,971,499, the grooves are formed in the panel support faces of the flange portions adjacent the pilot portion and the grooves include a bottom wall parallel to the end face of the pilot portion and the panel support faces of the flange portion, the outer groove wall is inclined toward the pilot portion and the inner groove wall is inclined outwardly toward the flange portion forming a “re-entrant groove.”
The back face of the self-attaching female fastener may also include linear wire grooves which receive linear frangible connector elements as disclosed in U.S. Pat. No. 3,711,931, also assigned to the predecessor in interest of the assignee of this application. The self-attaching nut disclosed in this patent is generally T-shaped in cross-section, wherein the grooves are formed in the side faces of the pilot portion. Self-attaching female fasteners may also be formed by cold header techniques, wherein the self-attaching female fastener is generally round, the flange portion typically surrounds the pilot portion and the groove is formed in the panel support face of the flange portion adjacent to and surrounding the pilot portion as disclosed, for example, in U.S. Pat. Nos. 3,810,291 and 3,878,599 assigned to the predecessor in interest of the assignee of this application. The self-attaching female fastener of this invention is preferably a rolled self-attaching female fastener of the type disclosed in the above-referenced U.S. Pat. No. 4,971,499. However, the self-attaching female fastener of this invention may also be formed by cold header techniques, wherein the flange portion surrounds the pilot portion as described above.
As set forth above, the applications for a self-attaching female fastener of the type disclosed herein are limited by the range of panel thicknesses. For example, a pierce nut of the type disclosed in the above-referenced U.S. Pat. No. 4,971,499 having an 8 mm diameter bore is 0.64 to 1.65 mm and a maximum panel thickness for the largest self-attaching female fastener of this type is 2.79 mm. If the self-attaching fastener is installed in a metal panel having a thickness of greater than 2.79 mm, there is little or no retention of the fastener to the panel and the thread cylinder is deformed or collapses during the installation. As used herein, the term “thread cylinder” refers to the bore of the fastener, whether or not the bore is internally threaded. There is, therefore, a long felt need for a female self-attaching fastener which may be installed in a thick or heavy metal panel having a thickness greater than 2.79 mm for many applications, particularly including automotive applications.